That's incredibly cynical and dark. Is that a theory or an hypothesis seeking proof (evidence)? I don't believe a conspiracy like that could survive.
I don't think I could go that far. I could see where teachers would want more docile kids, and therefor are more prone to "see" "Problems" where there are merely issues that need to be overcome. They in turn recommend psychiatry, telling parents how great other kids do on the drugs and so on. Psychiatrists are then put under pressure from parents who want smart, attentive kids and besides, the diagnostic factors for some of these diseases seem pretty broad from what I know of them - but I am no expert. Tell me, before these drugs, how many "boys would be boys"? Heck perhaps it is the urbanization of kids that make them ADHD, for lack of external (outdoor) stimuli? Just guessing here, but can kids learn to be patient in a culture full of cars & highways, fast food , rapid edits on films and videos, video games etc as compared to, say, waiting for that fish to nibble on the bait, reading a book, watching the stars and clouds, climbing trees, hiking, biking... but I suppose that is slightly off point, or upstream if you will.
Perhaps the example on this thread is a good jumping off point. I was asked what I first thought of when I heard the word 'bird', and I thought of a slang use that also had a secondary ironic attachment to it - a flapper. Every mind works differently, but I accept there is no way any teacher can figure out each mind they are entrusted. It is up to the kids and parents to find out how their minds work, and to develop approaches to learning that suit those minds.
Which is just yet another reason why we cannot, should not have these massive public school systems. Kids need to have their individual talents nurtured, and it is not possible if everything is rigid, structured or taught from rote. But again I digress... perhaps I am ADHD too :-)
Aside - I'm glad you didn't teach me, I might have gotten in more trouble than I did as a kid. {;^)